1. Field of the Invention
The invention relates to an electricity storage device including a plurality of battery stacks, each including a plurality of cells, and to a vehicle including the same.
2. Description of Related Art
A plurality of battery stacks are mounted on a vehicle or the like in some cases. The battery stack is formed by aligning a plurality of unit cells in one direction and outputs energy that is used to drive the vehicle. When a plurality of battery stacks are used, the plurality of battery stacks are aligned in the same plane (see Japanese Patent Application Publications Nos. 2005-019231, 2006-100156, and 2009-181896 (JP-A-2005-019231, JP-A-2006-100156, and JP-A-2009-181896), for example).
When a plurality of battery stacks are used, the plurality of battery stacks are aligned in the vertical direction in some cases. The plurality of battery stacks are arranged so as to intersect each other when viewed from above in some cases. In such a case, the heat generated by the lower battery stack(s) can rise and reach the upper battery stack(s).
When the plurality of battery stacks are arranged so as to intersect each other, the heat from the lower battery stack(s) reaches part of the upper battery stack(s) only. In other words, the upper battery stack(s) include(s) a unit cell that is affected by the heat from the lower battery stack(s) and a unit cell that is not affected by the heat therefrom. In this case, nonuniformity of temperature in the unit cells occur in the direction of alignment of the upper battery stack. When the nonuniformity of temperature in the unit cells occurs, there is a fear that nonuniformity also occurs in the deterioration conditions of the unit cells.